C/E/X PA Flat to 30 (FT30) PA TH Awesomeness

[Djim]

But like I said, that's only in a world without power compression

[CRESCENDO]

OK, so both "Xlim -7dB for continue power" and "Xlim -4dB for max power" need to be calculated WITH power compression numbers to know the true wattage of "continuous" and "max" power, right?

[Djim]

Originally Posted by CRESCENDO

OK, so both "Xlim -7dB for continue power" and "Xlim -4dB for max power" need to be calculated WITH power compression numbers to know the true wattage of "continuous" and "max" power, right?

Nope, the power compression you need to be subtracted from the true wattage (AES power rating or Xlim -7dB) to calculate the true SPL outcome. So for instance if you calculated with HornResp a driver needs 1000watt to generate 130dB you need to calculate the power compression figure and distract it from the 130dB.

You can calculate the figure of power compression with HornResp. By using the concept I gave you earlier -> AES power = Xmax.
So to calculate power compression you look to the difference between HornResp prediction and the fact AES power = Xmax.

I'll give you an example in my next post...

[Djim]

We know that a well engineered balanced PA drivers should reach its Xmax at AES power rating. So in case of the 18Sound 18LW2400 with a Xmax of 9,5mm should be reached at 1200Watt (AES power rating). Lucky for us 18Sound (is the only brand who) shares power compression figures for their drivers. In case of the 18LW2400 it suffers from 2,2dB at AES full power (1200W).

We also know the Re of the driver which is 5 Ohm. If you use this calculator you can calculate Eg (HornResp Voltage Input parameter) 1200W at 5Ohm = 77,46V for this driver.

If you use Xoc1’s TH18 HornResp input as an example you will see at 1200 watt (77,46V) the excursion reaches 12,3482mm at 48Hz.




The real Xmax is however 9,5mm so we need to lower the excursion with 2.8482mm in the HornResp excursion Graph. With trial and error you can find out Eg needs to be set at approx 59,6V to reach 9,5mm. Use the same calculator again to find out that 59,6V and 5 Ohm means 710W




Now we can calculate how many dB’s the difference is between 710W and 1200W.

1200 : 760 = Factor 1,69

Use the following calculator to calculate the factor of 1,69 into dB's.
You will read 2,28dB. If you compare that to the factory specs given for power compression (2,2dB) you can see how close it is.

I know I'm a terrible teacher but I tried to make it as simple as possible without using difficult formula's...

[olsound]

Originally Posted by Djim

We know that a well engineered balanced PA drivers should reach its Xmax at AES power rating. So in case of the 18Sound 18LW2400 with a Xmax of 9,5mm should be reached at 1200Watt (AES power rating). Lucky for us 18Sound (is the only brand who) shares power compression figures for their drivers. In case of the 18LW2400 it suffers from 2,2dB at AES full power (1200W).

We also know the Re of the driver which is 5 Ohm. If you use this calculator you can calculate Eg (HornResp Voltage Input parameter) 1200W at 5Ohm = 77,46V for this driver.

If you use Xoc1’s TH18 HornResp input as an example you will see at 1200 watt (77,46V) the excursion reaches 12,3482mm at 48Hz.




The real Xmax is however 9,5mm so we need to lower the excursion with 2.8482mm in the HornResp excursion Graph. With trial and error you can find out Eg needs to be set at approx 59,6V to reach 9,5mm. Use the same calculator again to find out that 59,6V and 5 Ohm means 710W




Now we can calculate how many dB’s the difference is between 710W and 1200W.

1200 : 760 = Factor 1,69

Use the following calculator to calculate the factor of 1,69 into dB's.
You will read 2,28dB. If you compare that to the factory specs given for power compression (2,2dB) you can see how close it is.

I know I'm a terrible teacher but I tried to make it as simple as possible without using difficult formula's...

THis is some good information.
Tell me more.

[Djim]

Second example:

Now I’ll take the RCF LF18N451 as example. The Xmax is 8,8mm and should be reached with 1500W (AES power rating). Use the first calculator to calculate the Eg Voltage for 1500 watt at 5 Ohm (Re driver). The outcome is Eg = 86,60V.

The excursion at 86,6V of the LF18N451 in Xoc1’s TH18-2 = 12,0918mm

So, again we lower the voltage until we reach 8,8mm. You will see it will need approx 63,05V.

Use the calculator again to find out 63,05V and a Re of 5Ohm = 795W.

500 : 795 = Factor 1,89.

Use the second calculator and you’ll find out this RCF suffers from 2,76dB at 1500 watts at 48Hz in Xoc1’s cab.

And you can use this for every driver that works in the corresponding TH, basreflex or 6th order bandpass. The only rules are the Fs of the driver needs to be lower than the Fb of the system and power rating should be given in AES standards...

[Zero D]

@ Djim

Lucky for us 18Sound is the only brand who shares power compression figures for their drivers

Hi, actually more manufactures than in previous years are, & have been providing PC data for some time now Here's several more that do.

Beyma/Fane/Precision Devices/Selenium

Thats just a quick list i put together, so expect to see more from other manufactures as well.

PC is often overlooked, or not known about, by a lot of people, which more times than not, leads to them wondering why their system doesn't sound as loud as they thought it would, even when throwing lots of power into it. And that's one of the reasons they blow them up !

So it's nice to see you providing some good info etc on the subject for folks.

[olsound]

So how much the rcf21 suffers.

[Djim]

Originally Posted by Zero D

@ Djim
Hi, actually more manufactures than in previous years are, & have been providing PC data for some time now Here's several more that do.

Beyma/Fane/Precision Devices/Selenium

Thats just a quick list i put together, so expect to see more from other manufactures as well.

PC is often overlooked, or not known about, by a lot of people, which more times than not, leads to them wondering why their system doesn't sound as loud as they thought it would, even when throwing lots of power into it. And that's one of the reasons they blow them up !

So it's nice to see you providing some good info etc on the subject for folks.

Thanks Zero D and I didn't know the other brands you mentioned also released these numbers for 'public domain use'.

[Djim]

Originally Posted by olsound

So how much the rcf21 suffers.

I gave you a complete worked out method and the calculating tools, so now its your turn Olsound!